Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$105.47	5.730%	$111.5134	$111.51	$111.50	$111.50
Purchase #2	$18.93	4.374%	$19.758	$19.76	$19.75	$19.80
Purchase #3	$150.47	9.124%	$164.1989	$164.20	$164.20	$164.20
Purchase #4	$26.90	11.121%	$29.8915	$29.89	$29.90	$29.90
Purchase #5	$235.41	8.703%	$255.8977	$255.90	$255.90	$255.90
Purchase #6	$89.82	8.654%	$97.593	$97.59	$97.60	$97.60
Purchase #7	$25.44	11.369%	$28.3323	$28.33	$28.35	$28.30
7 purchase totals =	$652.44		$707.1848	$707.18	$707.20	$707.20